Turbidimeter



. so, 1958 H. R. VEIT 2,866,379

TURBIDIMETER Filed Feb. 18, 1957 F0. Pwr

ArIrQAJA/fy United States Patent Otlice 2,866,379 Patented Dec. 30, 1958 TURBIDIMETER Heinrich Rudolf Veit, Berlin-Zehlendorf, Germany, assignor to Askania-Werke A. G., a corporation of Germany Application February 18, 1957, Serial No. 640,784

4 Claims. (Cl. 88-14) This invention relates to a turbidimeter, particularly for measuring turbidity in long-lasting, continuous or intermittent operations as distinguished from the more or less momentary immersion of a measuring device as in the well-known methods of oceanography. A typical eX- ample for some of the cases wherein the new instrument is useful is furnished by the supervision of euents and other ows in the treatment of sewage or industrial wastes.

The object of the invention is to counteract, minimize or eliminate measurement-distorting tendencies arising from the long-lasting service of the instrument and more especially to provide effective window-cleaning means for certain windows forming part of the instrument, irnmersed in the fluid under observation. The details will appear readily from a perusal of the specication which follows.

The sole figure of the drawing is a schematic, central, vertical section through an instrument embodying the invention.

A light source 1 such as an incandescent lamp energized through conductors in a cable, not shown, emits light which is collected by a lens 2 to illuminate, through a vertical window 3, the lluid or liquid to be inspected. The window forms part of the enclosure 3a of a closed casing 3b containing the lamp 1 and lens 2; and there may be provided a body 3c of desiccant, to keep the air in said casing free of humidity which might condense on the inside of window 3 under the influence of variable temperatures to which the instrument is exposed.

A similar casing 4a, opposite window 3, has a window 4 and contains a further lens 5, aperture plate 6 and photoelectric cell '7, the latter having connecting leads, not shown, which may run through the aforementioned cable. The windows 3, 4 as shown are parallel to one another and spaced by a small space 8a for circulation of turbid fluid.

According to the invention provision is made for the be described or shown herein. It has further been found necessary to make sure that, regardless of the various adjustments of switch 14, motor 13 is always stopped in a position wherein wiper is withdrawn from windows 3 and 4; therefore the motor circuit includes, in parallel with the time switch 14, a shunt switch 15 which is normally closed but which is opened by an extension of use of window wiper means for the fluid-contacting sides i of the windows 3 and 4, in space 8a, such means being shown at 8. In the measurement of turbidity in waste waters, where such a cleaning device is particularly important because of the manifold types of impurity present and the long periods 'of immersion which are common, it is further usual to make the distance between the illuminating and illuminated windows 3, 4 fairly short, for instance about one-half of an inch to six inches; and it is therefore preferred to use a single, unitary wiper means for both mutually facing windows 3 and 4.

A vertical rod 9'centered between the vertical windows 3, 4 serves to raise and lower the window wiper unit 8, under the influence of a link 10 driven by a pitman 11 on the crank 12 of a motor 13, in a closed housing 13a which may be superimposed on the lamp and photocell housings 3a, 4a. A time switch 14 is provided in housing 13a and connected to energize and deenergize the wiper motor 13 during suitable, adjustably predetermined time intervals, by well-known provisions which need not rod 9 each time that the wiper and rod are in their uppermost positions. Thus, assuming that the time switch 14 has been opened, the motor 13 remains energized until it has safely raised and withdrawn the wiper; at that moment-usually a fraction of a second after the opening of the time switchthe motor is stopped.

I have found it preferable to provide the wiper unit 8 with two separate and rigidly interconnected sets of wiper blades 16, one set for each window, and to provide each set with a plurality of wiper blades above one another, said blades being made of a suitable rubber or rubber-like material. I have further provided an expandable rubber boot 17 or the like to separate the motor and time switch housing 13a from the space 8a for the fluid to be inspected while allowing the rod 9 to move in said housing and in said iluid. The uid may flow into said space 8a from a passage 18 between the windows 3, 4, although such structure may be eliminated in cases where the turbidity of the fluid is a type tending to settle. If such a structure is provided between the windows, it may be connected with any desired, cooperating structure, such as a pipe or an open collecting funnel, not shown, by a flange 19.

The operation of the device is simple. The light ux from source 1, directed by lens 2 and window 3 through the turbid iluid, is diminished in illuminance at a rate corresponding with the turbidity; the exact correspondence being some variant of the Rayleigh scattering formula or of the other laws of illumination, dependent on size, form, arrangement and nature of particles, color filter effects and the like. These details need not be elaborated upon in this disclosure; they can and must be determined in each case, in accordance with principles known to the art. The important thing is, to avoid distortion of the illuminance incident through window 4 and system 5, 6 on the photocell 7, by deposition, growth or other accretion of dirt in space 8a; this is achieved by the window wipers 16, at a time cycle suitably determined in each case by the time switch 14. In a secondary way it is important, of course, to avoid gross interference with the light measuring process by the window wiper itself; this is achieved by the automatic position control, readily provided by rod 9 and shunt switch 15.

I claim:

l. In a turbidimeter, illuminating means having a iirst, vertical window with one surface in the fluid to be inspected; illuminance measuring means having a second Vertical window with one surface in said Huid opposite and parallel with the first window; a single window wiper for said windows; linkage actuating said wiper in recipro cating motions passing over and slightly beyond said windows; a motor actuating said linkage; a circuit for said motor; and a control system in series with said motor and comprising a time switch in said circuit and a normally closed shunt switch in said circuit and parallel with the time switch; said linkage being adapted to open said shunt switch only at a time when the linkage withdraws the wiper from the windows to the position slightly beyond the same.

2. A turbidimeter as described in claim 1, wherein said wiper comprises a single, rigid member carrying a plurality of superposed wiper blades on each side thereof, in contact with said respective windows.

3. A turbidimeter as described in claim 1 wherein said 2,866,379 s s 4 linkage comprises a reciprocating rod directly connected References Cited'in the file of this patent to said wiper and cooperating with the shunt switch.

4. A turbidimeter as described in claim 3 wherein said UNITED STATES PATENTS rod has an expandable member secured thereto and Sep- 1,937,721 Simon et al. Dec. 5, 1933 arating said uid from said motor, time switch and shunt' 5 1,969,627 Simon et al. Aug. 7, 1934 switch. 

